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James Webb Telescope

Skeptic Ginger said:
But there would have been billions of light years for them to move and create that motion blur.

But never mind, I'm getting a clearer picture of the issue now.
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Galaxies have their own intrinsic motion separate from the expansion of space, known as peculiar velocity.

https://en.wikipedia.org/wiki/Peculiar_velocity

It could be with the Hubble flow, or against, or lateral to it, but it's usually small enough it'll be a small component of its overall velocity. Plus we'd have to watch it for a really long time to actually see it move. Like, a million years.
 
Skeptic Ginger said:
So if they are in an expanding space I can see why they aren't getting closer to us but why isn't there a blur of light from their moving to the left or to the right as space expands?
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Motion blur is the result of multiple factors. Speed, distance and the length of the exposure. The closer you are to a moving object the faster it appears to be moving to our eyes. Take the ISS for example. It is traveling at about 17,500 mph at an altitude of about 1.3 million feet. Yet a jet aircraft traveling at 450 mph at 20,000 feet would appear to be moving much faster. Also, the cameras on the JWST can simply shorten the length of
the exposure to avoid motion blur if it needed to. Actually the problem is more the opposite. They need to collect as much light as possible to see things farther away so they lengthen the exposure.
 
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I watched (mostly fast forwarded through) the absolutely ridiculous NASA presentation of the JWST big reveal. They should have borrowed the Jan 6 Committee production crew. :rolleyes: They managed to stretch out 6 images into an hour presentation. They bounced around to different locations as if they needed to show how many people were involved.

The opening said it all. Some woman came out to the live audience and after they clapped she asked them to clap again. Then half the program was all about the telescope. It was stuff everyone has seen by now. I wonder if they did a focus group where everyone they were going to reveal the photos to didn't have a clue about astronomy.
 
Is a photon emitted from 2 light years away a year older than a photon emitted from 1 light year away when received?
 
ynot said:
Is a photon emitted from 2 light years away a year older than a photon emitted from 1 light year away when received?
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Not in any discernible way.

Assuming they are both emitted with the same energy, the one that traveled farther would impart less force due to the inverse square law. But that's about it (for a single photon).

AFAIK.
 
Mike Helland said:
Not in any discernible way.

Assuming they are both emitted with the same energy, the one that traveled farther would impart less force due to the inverse square law. But that's about it (for a single photon).

AFAIK.
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If the photons were emitted at the same time, wouldn’t the 2 light year distance emitted photon take a year longer to be received than the 1 year distance emitted one? If so, that would be discernible.
 
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ynot said:
If the photons were emitted at the same time, wouldn’t the 2 light year distance emitted photon take a year longer to be received than the 1 year distance emitted one? If so, that would be discernible.
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That seems to be part of the answer to the question of how we calculate the distance of astronomically far objects. Can that be resolved to a few years?
 
Skeptical Greg said:
That seems to be part of the answer to the question of how we calculate the distance of astronomically far objects. Can that be resolved to a few years?
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For near enough things we can use parallax from the Earth's motion to tell distances.

For much farther things, we use the redshift in the spectra of a galaxy to estimate distance, but the margin of error is more than a few years. But more importantly, that cannot be done with a single photon. You need enough photons from the entire spectrum to see how far the absorption lines have shifted.

Again, based on what I know, which isn't a ton. Corrections welcome.
 
ynot said:
If the photons were emitted at the same time, wouldn’t the 2 light year distance emitted photon take a year longer to be received than the 1 year distance emitted one? If so, that would be discernible.
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If you knew that kind of stuff ahead of time, sure.

If you know when the photons were emitted, the distance they have to travel, and their energy, sure.

But you don't know those things when you're just detecting photons.
 
Mike Helland said:
If you knew that kind of stuff ahead of time, sure.

If you know when the photons were emitted, the distance they have to travel, and their energy, sure.

But you don't know those things when you're just detecting photons.
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The answer is “sure” regardless of what we knew/know. I'm asking what would be the case in reality. No need for humans to be involved at all. Imagine the photons where received by dinosaurs (or a rock) if you like.
 
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Blue Mountain said:
Overall I agree with your sentiment, but the JWST actually has not cost all that much. The current cost is estimated at $US 9.7 billion. But that spans a very long time, from the project's start in 1998 to the end of its proposed 5 year mission in 2027—and barring unforseen problems it could well operate for 10, 15, or even 20 years. Even assuming only a 5 year mission, that's $9.7 billion over 29 years, or a "mere" $803 million a year.
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So, wait. Are you saying that JWST has a five year mission to explore strange new worlds?
 
Reformed Offlian said:
So, wait. Are you saying that JWST has a five year mission to explore strange new worlds?
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I think after the first ding there was some talk about the expected lifetime of the mirrors.

At first the goal was to see as far back in time as they could. But back before 2019 they added searching the atmospheres of exoplanets to the mission.

JWST will search the atmospheres of exoplanets for signs of alien life
We are two scientists who study exoplanets and astrobiology. Thanks in large part to next-generation telescopes like James Webb, researchers like us will soon be able to measure the chemical makeup of atmospheres of planets around other stars. The hope is that one or more of these planets will have a chemical signature of life.
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