4 ms·

That's not how relativistic speeds work. If this was going near enough to the speed of light, it could travel almost any distance before decaying. Time dilation

That's not how relativistic speeds work. If this was going near enough to the speed of light, it could travel almost any distance before decaying. Time dilation would be observed of the particle, where it would appear that time is ticking slower for the particle compared to our own frame of reference.

chunky1994 10y ago
Actually what the parent comment said would be correct. Time dilation and length contraction do not arbitrarily change the proper distances that particles travel at near light speeds. As observers, the detectors would see precisely what we expect if we calculate the distance using the detector's proper time when compared with the distance we experimentally measure.
- amelius 10y ago
  Please explain why you think this is so.
- russdill 10y ago
  This is super basic stuff https://en.wikipedia.org/wiki/Time_dilation_of_moving_particles https://en.wikipedia.org/wiki/Time_dilation_of_moving_partic...
  - nitrogen 10y ago
    The linked wiki article says that rapidly moving particles take longer to decay.
- gus_massa 10y ago
  Mmm... I have the strange feeling that you both agree, let's write this with more details to avoid confusion. The half life of a static tetraneutron is (theoreticaly) 5E-22s. If you are at a laboratory and the tetraneutron is moving at relativistic speed, the apparent half life in the laboratory frame will increase substantially. To calculate the distance that the tetraneutron will travel you must multiply the velocity x the apparent half life. I.E d ~= v * 1/(1-v^2/c^2) * t_hl where t_hl = 5E-22s = the half life of the tetraneuton not the classic version that is d_clasic_wrong = v * t_hl For a more detailed explanation, with numbers and graphic you all can see the analogue experiment with muons: http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html -- Anyway, IIRC a half life of 5E-22s is still very small. IIRC you can use a bubble chamber or something similar to see the trajectory of the particles. You can only see a collision and examine the debris and you will note that when the collision has some specific energy you will get an unexpected excess of collisions. You only can examine the direction and energy of the debris to make a good guess of the intermediate steps of the collision and discover that for a very short time you had a tetraneutron.
  - chunky1994 10y ago
    I do agree that time dilation occurs, what I disagreed with/corrected was with this: it could travel almost any distance before decaying, which I took to imply that the lengthening of particle lifetimes was not measurable in the way that you just pointed out. In retrospect perhaps the parent comment was saying theoretically it could travel any distance which is true, but doesn't really help in estimating whether it could clear nuclear radii or not.
twic 10y ago
That's a good point, i didn't think of that! Do we know how fast the tetraneutrons were moving in this experiment? If so, we can work out the degree of time dilation, and how far it would have got.

chunky1994 10y ago

Actually what the parent comment said would be correct. Time dilation and length contraction do not arbitrarily change the proper distances that particles travel at near light speeds. As observers, the detectors would see precisely what we expect if we calculate the distance using the detector's proper time when compared with the distance we experimentally measure.

amelius 10y ago
Please explain why you think this is so.
russdill 10y ago
This is super basic stuff https://en.wikipedia.org/wiki/Time_dilation_of_moving_particles https://en.wikipedia.org/wiki/Time_dilation_of_moving_partic...
- nitrogen 10y ago
  The linked wiki article says that rapidly moving particles take longer to decay.
gus_massa 10y ago
Mmm... I have the strange feeling that you both agree, let's write this with more details to avoid confusion. The half life of a static tetraneutron is (theoreticaly) 5E-22s. If you are at a laboratory and the tetraneutron is moving at relativistic speed, the apparent half life in the laboratory frame will increase substantially. To calculate the distance that the tetraneutron will travel you must multiply the velocity x the apparent half life. I.E d ~= v * 1/(1-v^2/c^2) * t_hl where t_hl = 5E-22s = the half life of the tetraneuton not the classic version that is d_clasic_wrong = v * t_hl For a more detailed explanation, with numbers and graphic you all can see the analogue experiment with muons: http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html -- Anyway, IIRC a half life of 5E-22s is still very small. IIRC you can use a bubble chamber or something similar to see the trajectory of the particles. You can only see a collision and examine the debris and you will note that when the collision has some specific energy you will get an unexpected excess of collisions. You only can examine the direction and energy of the debris to make a good guess of the intermediate steps of the collision and discover that for a very short time you had a tetraneutron.
- chunky1994 10y ago
  I do agree that time dilation occurs, what I disagreed with/corrected was with this: it could travel almost any distance before decaying, which I took to imply that the lengthening of particle lifetimes was not measurable in the way that you just pointed out. In retrospect perhaps the parent comment was saying theoretically it could travel any distance which is true, but doesn't really help in estimating whether it could clear nuclear radii or not.

twic 10y ago

That's a good point, i didn't think of that! Do we know how fast the tetraneutrons were moving in this experiment? If so, we can work out the degree of time dilation, and how far it would have got.