Ask Science
Ask a science question, get a science answer.
Community Rules
Rule 1: Be respectful and inclusive.
Treat others with respect, and maintain a positive atmosphere.
Rule 2: No harassment, hate speech, bigotry, or trolling.
Avoid any form of harassment, hate speech, bigotry, or offensive behavior.
Rule 3: Engage in constructive discussions.
Contribute to meaningful and constructive discussions that enhance scientific understanding.
Rule 4: No AI-generated answers.
Strictly prohibit the use of AI-generated answers. Providing answers generated by AI systems is not allowed and may result in a ban.
Rule 5: Follow guidelines and moderators' instructions.
Adhere to community guidelines and comply with instructions given by moderators.
Rule 6: Use appropriate language and tone.
Communicate using suitable language and maintain a professional and respectful tone.
Rule 7: Report violations.
Report any violations of the community rules to the moderators for appropriate action.
Rule 8: Foster a continuous learning environment.
Encourage a continuous learning environment where members can share knowledge and engage in scientific discussions.
Rule 9: Source required for answers.
Provide credible sources for answers. Failure to include a source may result in the removal of the answer to ensure information reliability.
By adhering to these rules, we create a welcoming and informative environment where science-related questions receive accurate and credible answers. Thank you for your cooperation in making the Ask Science community a valuable resource for scientific knowledge.
We retain the discretion to modify the rules as we deem necessary.
view the rest of the comments
But things are actually moving.
The movement causes light emitted from those things to redshift, like the siren of an ambulance changing its pitch when it's moving away from you. And stars we can currently still see will disappear in the future, never to be seen again, as they move outside of our observable universe, accelerating faster away from us than the light they emit.
That's the thing. Nothing is actually moving, it just appears to be. Space itself is increasing in volume.
The best analogy isn't that everything's moving, it's that everything's shrinking.
If you and a friend are stood 2 metres apart and you suddenly both shrink, proportionately, to half your height, the distance between you is going to appear to have doubled, when in fact it's still 2 metres.
Universe expansion turns this on its head by the distance itself growing to 4 metres without either of you moving.
As to why this doesn't happen on local scales: gravity has a tendency to hold nearby things together. And closer still, atomic forces.
For now. As I understand it eventually space will be so stretched out even atoms will degenerate.
i thought distance caused red-shift.. prolly semantics.. but ... do 2 stationary objects on an expanding plane 'move'?
An observer perceives them as moving objects, i.e. they appear to move, but they actually don't, as it's the space between them that expands.
I always thought it was more like, since light can act as a wave, it is like the wave is becoming stretched out as the space expands which creates that redshift. The light isn't moving any faster or slower, but it has a redder (lower energy) frequency. Like a plucked string that is pulled more taut as the space in between expands. It essentially loses energy, and at some point that energy loss will be significant enough for light from other galaxies no longer being detectable for us. As well as any new light emitted from them simply not being able to overcome the distance+expansion speed.
There is just more space being added in between us and them, as if we were on a plane of stretchy fabric or on the surface of a balloon being blown up. From their (the other galaxy's) perspective, we are doing the same exact thing, as well as every other thing that is observable to them.
*words of someone who is not an astronomer, nor a scientist.