Hubble's law

[anthrax]

Can someone explain in layman term why the recessional velocity of a galaxy is proportional to its distance (to some point)?

 

[samoth]

Hmm... with or without any math?

If I/someone else dosen't get to this today, I'll make sure to do it tomorrow.

 

[anthrax]

Hmm... with or without any math?

If I/someone else dosen't get to this today, I'll make sure to do it tomorrow.

Watherver as long as it doesn't require to have Hawking's knowledge to understand it

Question #2: Can we reproduce (at CERN for example) energy --> matter + anti-matter ?
and what is the ratio matter/anti-matter

 

[redguru]

You do know what a doppler shift in apparent frequency is, right? Like when a train passes by and the pitch is higher as it approaches and lower as it recedes? Well, light has a shift to infrared as the deep space object recedes from us. We can plot that apparent shift in the light spectrum that reaches us and calculate the deep space object's distance from us by the relationship of the velocity vs distance of known distant objects.

Does that help?

 

[anthrax]

You do know what a doppler shift in apparent frequency is, right? Like when a train passes by and the pitch is higher as it approaches and lower as it recedes? Well, light has a shift to infrared as the deep space object recedes from us. We can plot that apparent shift in the light spectrum that reaches us and calculate the deep space object's distance from us by the relationship of the velocity vs distance of known distant objects.

Does that help?

I understand how we can calculate it
But is this recessional velocity not constant?

 

[redguru]

I understand how we can calculate it
But is this recessional velocity not constant?

Different objects are moving at different rates away from us, We are all moving outwards from the center of the universe, but two objects that are on parallel paths would look nearly stationary.

You could do the old balloon experiment, blow it up halfway and place dots randomly on the shell. Blow it up completely and note the change in spatial relationships between all the dots.

 

[anthrax]

Different objects are moving at different rates away from us, We are all moving outwards from the center of the universe, but two objects that are on parallel paths would look nearly stationary.

You could do the old balloon experiment, blow it up halfway and place dots randomly on the shell. Blow it up completely and note the change in spatial relationships between all the dots.

Fromm what I understand if a galaxy is at a distance d from us, its recessional velocity will be half of another galaxy at a distance 2d

and the same galaxy will move away from us faster with time (and distance)

 

[redguru]

Fromm what I understand if a galaxy is at a distance d from us, its recessional velocity will be half of another galaxy at a distance 2d

and the same galaxy will move away from us faster with time (and distance)

I'm sorry, In your original question I was thinking closer objects than galaxies. Ignore my ignorance.

Your first point would be correct because distance and velocity are directly proportional and only differ by the Hubble Constant. V = H*D, where V is the red shift calculated velocity of the object, H is the hubble constant and D is the galaxy's distance from our point of reference. We don't quite know D we can only approximate through brightness and angular size of the galaxy indirectly. Therefore it is hard to pin down H.

The Balloon experiment will show you your second point.