Total: 413, showing: 1 – 20

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

@ilza: I'll tear up my engineering degree and tell Lawrence Krauss he's a quack. Thank you for setting us straight.

Link | Posted on Apr 6, 2021 at 22:09 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

"does rocket just outside EH see same thing as Earth observer sees 1 month later"

The Earth will appear blueshifted (higher frequency) to the rocket. The laser coming from from the rocket will appear redshifted (lower frequency). The degree to which will depend on the actual distance to the event horizon. There will be time dilatation, so 1 month for the rocket is not 1 month for Earth (longer for Earth).

Link | Posted on Apr 6, 2021 at 22:08 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

"So, in your educated opinion, the situation of “a moving black hole” differs from an object falling to a stationary black hole? Yeah, right!"

At time T = 0, black + object at distance X with no relative motion. The object will vanish at time T1.

At time T=0, same black hole + object at distance X, but with a relative motion towards each other. The object will vanish at time T2.

T2 < T1.

Link | Posted on Apr 6, 2021 at 21:02 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

Consider objects approaching the cosmic horizon (which is identical to objects approaching any horizon):

"Objects therefore appear exponentially redshifted as they approach the horizon. Finally, their apparent brightness declines exponentially, so that the distance of the objects inferred by an observer increases exponentially. While it strictly takes an infinite amount of time for the observer to completely lose causal contact with these receding objects, distant stars, galaxies, and all radiation backgrounds from the Big Bang will effectively “blink” out of existence in a finite time – as their signals redshift, the time scale for detecting these signals becomes comparable to the age of the universe"

Life, The Universe, and Nothing: Life and Death in an Ever-Expanding Universe

Lawrence M. Krauss and Glenn D. Starkman

arXiv:astro-ph/9902189v1

Link | Posted on Apr 5, 2021 at 17:35 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

<" THERE IS NO NOTION OF A MOVING OBJECT! Speed is a RELATIVE notion">

Your statement is an exercise in gibberish as are your other statements. Speed is the magnitude of relative motion. To say that motion doesn't exist is to say that objects can't have relative speed. A moving black hole is moving relative to an observer/object, the magnitude of which affects the equations of motion.

Link | Posted on Apr 5, 2021 at 17:17 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

An expanding black hole is no different from a moving black hole: it simply changes how fast an infalling object approaches the event horizon. If a lot of matter is falling into a black hole at once, that simply means the horizon is expanding and time dilation and photon energy approaches zero faster for such matter.

Also keep in mind that high energy particle jets at the poles of the black hole are necessarily NOT occurring in regions where time dilation approaches zero. These particles are accelerated to 99% of the speed of light, but this is only a 7x time dilation factor. The majority of particles never receive enough energy to escape or are on a trajectory into the black hole.

The time dilation of these particles increases very rapidly (7x -> 700 -> 7 billion -> 7 billion billion billion times, etc). These infalling particles become more and more "like" the event horizon they are approaching until the are indistinguishable from it (to an outside observer).

Link | Posted on Mar 30, 2021 at 16:51 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

The math says that as an object approaches the event horizon, the observed passage of time to an outside observer approaches zero. It will never reach zero but the distance will decrease exponentially (ie. the object will eventually "freeze" to outside viewers).

BUT, this also means the redshift approaches infinity (most people ignore this, leading to the confusion). Therefore the energy of any photon released when the object appears "frozen in time" exponentially approach zero to the outside observer. So no matter the energy level of the photon released, it will be finite and therefore approach zero to an outside observer (but not to the infalling object, photon energy depends on frame of reference).

Eventually even the most sensitive equipment will not be able to detect that photon and will be indistinguishable from the Hawkings Radiation, ie. the object is now indistinguishable from the back hole to an outside observer (ie. it is now part of the black hole).

Link | Posted on Mar 30, 2021 at 16:11 UTC

Jeff Greenberg: -----
we are told a space ship entering a black hole
would take forever from our point of view;
why isn't this true for ALL matter?
why don't black holes take forever to grow bigger
than their original size???
(authoritative scientific minds appreciated)

It will take forever for you to "see" the matter cross the event horizon. From our point of view, rather than a "frozen image", the infalling matter becomes more and more red shifted and dimmer. This continues until the matter is essentially invisible because it will take an infinite amount of time to get that last infinitely red shifted photon from the matter crossing the horizon.

So take a 1 solar mass black hole (2.9 km radius black hole) and throw a 1 solar mass at it. Assuming all the matter goes into the black hole: the matter will be shredded, become more red shifted and dimmer until essentially undetectable, and the black hole will grow to 2 solar masses (5.9 km radius).

We will never "see" the matter fall in just like we can't "see" the event horizon. The "unseeable" region of space will grow to 5.9 km in radius.

Link | Posted on Mar 26, 2021 at 21:02 UTC

NickyB66: Let's hope humankind don't trash Mars like we are doing to Earth. Nice images.

Mars is fundamentally uninhabitable. We could fill Earth's oceans with garbage until we can walk on it, then detonate every nuclear warhead on Earth, then get hit with a dino-killer asteroid, and the resulting apocalyptic wasteland would still be a paradise for life compared to Mars. So I'm not sure how we'll "trash" Mars when its already trash.

Link | Posted on Mar 19, 2021 at 20:01 UTC

Psychfilms: Here's a philosophical question for photographers.... Does software like this cross the line between the true art of photography (think 'analog' as the standard) and photography as the basis for a graphic design?

In other words, would you feel comfortable providing a client or galley photographs that you took which were manipulated in the fashion available in this software?

It's a slippery slope with digital. First most all digital cameras 'process' an image in the camera based on its color science and settings (e.g. Fuji's film simulations), then there are simple post adjustments like saturation or contrast. Again the slippery slope of what you see with your eyes that you photograph and what the final presented image looks like. In some ways it's all good depending on your artistic intent. But on the other hand if you are a serious or professional photographer, does something not feel right with such manipulation? Cheers!

There are fields of photography producing images for business purposes rather than art: website graphics, advertising, online/offline catalogs, product manuals, etc.

In that case It's important to understand and deliver what your client/employer wants. A business has no interest in the "true art of photography". There's no value in a photo being unaltered for sake of photography.

In some cases altered photographs will violate laws or create legal liabilities. In that case you need to understand the nuisances on what you can and can't deliver.

Ultimately, we can argue all day about the semantics of whether the altered surfer photo (above) is still a "photograph". But that's a meaningless discussion for a business that's creating a billboard... So you do your work, satisfy the client, move on to the next job and leave the semantics for the
forums.

Link | Posted on Mar 19, 2021 at 15:05 UTC

Adam007: Ballsy video. I hope Amazon doesn't bury their listings in response.

(I love Peak Design AND Amazon.)

I don't think Amazon cares. Amazon Basics and Peak Design products are aimed at different customers.

The average Amazon Basics customer is judging whether to buy the \$10 no-name bargain sling bag or the \$25 backed-by-Amazon bargain sling bag.

Peak Design is selling a more premium product that comes with a story on why purchasing their product makes you a better person (as told in the video). That's a different clientele from the Amazon bag, The existence of the Amazon "Basics" product actually helps Peak Design market its product as "premium". Its why the video was created.

Link | Posted on Mar 3, 2021 at 23:10 UTC

The price keeps rising for the Amazon bag (was \$27 a few minutes ago, now \$30 as I write this), which according to the Amazon algorithm means its selling well (possibly thanks to this article). It is also interesting how the negative reviews on Amazon are from Peak Design employees (confirmed via Linkedin).... lol.

Link | Posted on Mar 3, 2021 at 22:15 UTC as 162nd comment | 3 replies

Fazal Majid: Eco-friendly leather == cheap plastic.

In France it's illegal to label vegetarian substitutes for foods normally of animal origin using the same term, like "milk", "butter", "steak" or "mayonnaise". I don't know if the law also applies to leather. Now Gitzo is really an Italian company now, French no more.

It says "cruelty-free, environmental-friendly, and non-toxic synthetic leather". So its not real leather (veg or chrome tanned) and likely not a petroleum-based synthetic leather. It could be something like Pinatex (a cellulose-based synthetic leather).

Link | Posted on Mar 3, 2021 at 21:52 UTC

Horshack: I'm giving out a "Best Poster" award for comments to this article. Anyone interested in participating should submit \$10/USD to me. The enrollment period ends tomorrow at midnight. 1st place prize is \$75. 2nd place is a set of steak knives. 3rd place is you're fired.

I would laugh if one person enters. The OP will be out \$65....

Link | Posted on Feb 1, 2021 at 19:16 UTC

smashooter: I find it curious to watch many online photographers, including your guest shooter, use a rear LCD screen to compose photos while holding a camera at arm’s length. Even though she used a monopod and took advantage of the R5’s internal stabilization, it seemed that she had some trouble controlling the framing of her shots because of the weight of the lens. Using the camera’s eyepiece instead would have allowed her to control that weight more successfully, I think. Apparently the technique works for her and for many others, and you can’t argue with success, I guess, but it should be noted that the eyepiece has its uses.

@grahamho, "This criticism of a woman photographer"

You're the only one bringing gender into the discussion.

At 6:05 in the video you can see the camera sway back and forth. I picked up on that only because *I've* had to work through similar issues when using a monopod. Monopod technique is of interest to me, far more of interest than the performance of a lens I'll never own.

With F1.8, daylight, and the giant reflector that is snow, the swaying should cause no issue. But reduce the lighting and that swaying can effect the focus/sharpness. A monopod is not a tripod, but when braced against your eye, your legs and the monopod effectively creates a tripod.

Link | Posted on Feb 1, 2021 at 19:14 UTC

McArchive: "it amounts to a rough estimate of \$160,000 profit"
----
'noun: profit; plural noun: profits

a financial gain, especially the difference between the amount earned and the amount spent in buying, operating, or producing something.'
----
Unless or until you know their expenses, is it um fraudulent, or something, to roughly estimate their profit(s)? What if we look at the 'About this site,' will we find details about this author or sponsored content, or am I a both siderist now?

That said, these shows/contests/exhibits have a long, varied, and storied history, most folks recognize that. If memory serves, this is not the first time such questions have been reported on or asked on these pages which makes me wonder why you did last weeks bit before asking this weeks question.

Expense/profit has nothing to do with fraud. Most "contests" that require an entry fee (eg, lottery tickets, casinos) are bad value to the contestants and result in high profits for the operator. That doesn't make it fraud. Fraud is using deceit to obtain something of value.

If the contestants willingly gave the \$20 per entry free, the photos were all equally judged, and the promised prizes were given out, then there is no fraud. Perhaps fraud took place during the judging, but there isn't enough info given to say that occurred.

I agree that these types of awards are suspect and should not be publicized. But I suspect that most contestants knew the award was a bad financial investment. IMHO they probably enter many contests like this for that small chance to call themselves and "award winning" photographer.

Link | Posted on Feb 1, 2021 at 17:57 UTC

smashooter: I find it curious to watch many online photographers, including your guest shooter, use a rear LCD screen to compose photos while holding a camera at arm’s length. Even though she used a monopod and took advantage of the R5’s internal stabilization, it seemed that she had some trouble controlling the framing of her shots because of the weight of the lens. Using the camera’s eyepiece instead would have allowed her to control that weight more successfully, I think. Apparently the technique works for her and for many others, and you can’t argue with success, I guess, but it should be noted that the eyepiece has its uses.

I picked up on that as well. But as she said, the lens is much larger than what she normally uses (85mm?). So I suspect she's simply adapting her normal technique to an atypical situation. If you throw a 7 lb lens at somebody and film them use it for the first time, don't expect perfect form.

Link | Posted on Jan 28, 2021 at 20:37 UTC

Now we only need a Verneer painting of DPR's studio test scene so we can add him to the comparison tool. That way I can compare him against my 5Div. IMHO, Canon has the edge in sharpness.

Link | Posted on Jan 22, 2021 at 16:50 UTC as 10th comment

jxh: It's a good thing, simulation can help avoid dead ends, but it is not still not reality.

Feynman's statement still applies "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."

NOTHING beats real world testing.

(I spent a lifetime in both engineering and software development)

Previously, multiple prototypes would be developed during product development to test various ideas for feasibility. To use your example of scientific theory: the "theory" was developed piecemeal through multiple experiments.

Now, complete prototypes will be manufactured at the end of the development cycle to confirm the validity of the simulations. In other words, complete theories will be tested. So Mr. Feynman is still being respected.

The prior method is slow and costly. You're investing in materials, tooling, and manufacture that may be rendered obsolete by future testing. Take the desired body from one tested prototype, the desired sensor from another, and the result could be unexpected overheating.... oops, its too late in the development cycle and we're over budget on tooling so I guess we just limit the record times.

Link | Posted on Sep 30, 2020 at 17:10 UTC