How fast does gravity travel???

[Dork Lard]

The theory of an infinite universe was killed off by the Big bang theory and more concretely by the measurement of cosmic background radiation.

So, one theory cancels another theory?

That's a bit like saying one big lie cancels out all the other little lies.

I'm not saying big bang is a lie, that is way above my paygrade, but it is just a theory !

 

[IT Minion]

So, one theory cancels another theory?

That's a bit like saying one big lie cancels out all the other little lies.

I'm not saying big bang is a lie, that is way above my paygrade, but it is just a theory !

No, testable hypothesises that fail kill off theories. Like the Steady state theory that was killed off by Hubbles observations of an expanding universe.

Please remember that a hypothesis that can't be tested isn't a scientific theory. I don't know what you think the universe looks like but 'infinite' isn't compatible with the big bang theory.

 

[RandomGrinch]

If this universe of ours does not have infinite stars, could you please Google the theory of what is beyond the edge of where all the stars are.

...and if you haven't yet, have a good look at the absolutely beautiful deep field image from JWST.
...and I thought the Hubble deep field image was sublime!

Webb’s first deep field

Webb’s first deep field

www.esa.int

Edit:
...and a nice little visualisation of our galaxy at different wavelengths, from my neck of the woods!

Chromoscope

www.chromoscope.net

 

[Justin Passing]

...and I thought the Hubble deep field image was sublime!
https://www.esa.int/ESA_Multimedia/Images/2022/07/Webb_s_first_deep_field

Quite a lot of what looks like sagittal astigmatism in that pic. Anyone know more about that?

 

[Trazor]

It's unrealistic to believe that the universe is infinite.

If it were, there would be an infinite number of earths, as the universe would have an infinite amount of time to create them.

Also if the Universe was infinite, there would be an infinite number of stars, and the light would have an infinite amount of time to reach us,
therefore the night sky would be white.

 

[RandomGrinch]

Quite a lot of what looks like sagittal astigmatism in that pic. Anyone know more about that?

I think that you are noticing the 'diffraction spikes'?- (simplistically!) the six main ones are caused by the hexagonal shape of the mirror segments of the JWST, and the two smaller spikes caused by the secondary mirror supports.
(See page 23 of the attached for the science! ).
They are prominent on the image due to the foreground stars being very bright compared to the background (when it's the background that's really of interest).
This effect will only occur for a limited set of images (say deep fields, or where the effect can actually help with the mirrors calibration).
JWST itself is an anastigmat telescope - so hopefully shouldn't have astigmatism!

Webb's Mirrors - NASA Science

Video Overview What Kind Of Telescope Is Webb? Webb is what is known as a three mirror anastigmat telescope. In this configuration, the primary mirror is concave, the secondary is convex, and it works slightly off-axis. The tertiary removes the resulting astigmatism and also flattens the focal...

webb.nasa.gov

I hope that makes sense?

 

[Dork Lard]

Quite a lot of what looks like sagittal astigmatism in that pic. Anyone know more about that?

If you even know what that means . . . .

 

[Dork Lard]

It's unrealistic to believe that the universe is infinite.

If it were, there would be an infinite number of earths, as the universe would have an infinite amount of time to create them.

Also if the Universe was infinite, there would be an infinite number of stars, and the light would have an infinite amount of time to reach us,
therefore the night sky would be white.

Please tell me what is on the other side of the universe.

Infinite as a concept exists, most folk simply cannot comprehend it.

 

[Trazor]

Most folk simply cannot comprehend it.

No human can fully comprehend infinity.

We can't comprehend how “big” or “never-ending” it is, because our perception of time always has a beginning and an end.

Perhaps we can't understand the concept of nothing on the other side.

 

[Risteard]

9.81 meters per second squared is the acceleration due to gravity. Light travels at 2.99 x 10^8 meters per second. For those who prefer the imperial system, that is 32 feet per second squared, and 9.81 x 10^8 feet per second

In a vacuum. Through an atmosphere, e.g. the Earth's atmosphere, there is also drag. So eventually the forces cancel out and the object ceases to accelerate, hence the concept of "terminal velocity".

 

[Dork Lard]

No human can fully comprehend infinity.

I can, along with a few other folk.

 

[Justin Passing]

I think that you are noticing the 'diffraction spikes'?- (simplistically!) the six main ones are caused by the hexagonal shape of the mirror segments of the JWST, and the two smaller spikes caused by the secondary mirror supports.
(See page 23 of the attached for the science! ).
They are prominent on the image due to the foreground stars being very bright compared to the background (when it's the background that's really of interest).
This effect will only occur for a limited set of images (say deep fields, or where the effect can actually help with the mirrors calibration).
JWST itself is an anastigmat telescope - so hopefully shouldn't have astigmatism!

Webb's Mirrors - NASA Science

Video Overview What Kind Of Telescope Is Webb? Webb is what is known as a three mirror anastigmat telescope. In this configuration, the primary mirror is concave, the secondary is convex, and it works slightly off-axis. The tertiary removes the resulting astigmatism and also flattens the focal...

webb.nasa.gov

I hope that makes sense?

Thanks for the document, I hadn't seen that.
No not those spikes, those you get from the straight edges... Like in simple camera lenses with hexagonal diaphragms. ( for many years you could recognise Nikon photos because their lenses all had 9 blade irises). You can remove the effect in software - a process of deconvolution.
Astigmatism's different, I'll let you look it up if interested, there's tangential and sagittal.
I read that the JWT was an anastigmat earlier. I can only think the effect I'm referring to is something coming from object which aren't in focus. Anastigmatism is determined on the focus plane, points of of light in front can have say a radial blur and behind, a tangential one.

Here you can see several yellowish tangential and a couple of whitish radial.

If you do an image stack, you get both, producing a cross.

I haven't read much about the jwt yet, I expect it's explained somewhere.

 

[Justin Passing]

therefore the night sky would be white.

Some/many/most stars are moving away from us faster than c, so their light doesn't reach us. And there isn't an infinite number of stars inside the cone we can see. Also too as well, distant stars are too dim to see - intensity α 1/d² .

 

[Justin Passing]

In a vacuum. Through an atmosphere, e.g. the Earth's atmosphere, there is also drag. So eventually the forces cancel out and the object ceases to accelerate, hence the concept of "terminal velocity".

I checked, when I quoted for Dover cliffs above. Fatty the faller would need cliffs about 1.2 times their height, to get near terminal velocity. It's around 120mph. depending how fat fat fatty is.

Dork lard would go faster than that, on account of his density..

 

[Risteard]

I checked, when I quoted for Dover cliffs above. Fatty the faller would need cliffs about 1.2 times their height, to get near terminal velocity. It's around 120mph. depending how fat fat fatty is.

Dork lard would go faster than that, on account of his density..

Around 120mph in a stable belly to Earth position.