

The Oh My God Particle - mnemonicsloth
http://www.fourmilab.ch/documents/OhMyGodParticle/

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pmichaud
Summary: A particle (probably a proton) was detected hitting the atmosphere at
nearly the speed of light, which is kind of impossible or at least
implausible, and they can't figure out how it happened or where it came from.

My question is: are they sure their equipment didn't just have a glitch?

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mattheww
Short answer: glitch isn't the right word. There was almost certainly a
particle with an extremely high energy. Whether they can measure energies that
high is questionable.

Long answer: I'm not familiar with this specific experiment, but I am familiar
with ones that try to measure the same thing.

The thing about most of these devices is that they have a sweet spot in which
they have the highest accuracy. These detectors have a sweet spot which is a
few orders of magnitude below the energy measured here. So there is always the
question of how well you can extrapolate.

You'll notice there is no uncertainty quoted on the energy. It would not be
unreasonable to expect that uncertainty is at least 1 order of magnitude in
each direction. Probably more.

While that might seem like a lot, it's also important to know that the
relevant measurement is not the particle's energy, but actually the number of
particles above a certain energy. So they don't care so much if the energy
measurement is off by a lot, as long as it's really big.

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billforsternz
> And thus, approximately: v = 0.9999999999999999999999951 c

Okay.

>So taking 3×108 metres per second as the speed of light, we find that the
particle was traveling 2.9999999999999999999999853×108 metres per second,

Oh dear, that's a rather alarming piece of innumeracy. The speed of light is
approximately 3x10^8 metres per second, All those 9's in 2.999 etc would imply
the speed of light was exactly 3x10^8 metres per second which would be an
extraordinarily weird coincidence.

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jerf
The speed of light is exactly 299,792,458.0000000 (and so on) meters per
second. This is because this is actually the definition of the meter now, so
my string of "0"s that are significant digits is justified. 299,999,999.999...
is therefore superluminal and you are correct.

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scotty79
> Sokolsky has calculated that at 3×1020 eV, even a single proton could travel
> no farther than 10 megaparsecs

I wonder how fast proton looses energy (due to interactions with photons of
background radiation).

How much energy it would need to travel to us from edge of observable
universe?

Particle have (very short) wavelegths associated with them. It might be
interesting to observe larger amount of such high energy photons coming from
same point in the sky especially if there is a black hole near their path that
could bend it slightly. Maybe we could get some diffraction patterns. ... yeah
I'm probably insane.

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jackdawjack
The usual energy loss mechanism for cosmic-rays (fast protons) is reverse-
compton scattering off the cosmic-microwave background photons, which is quite
amazing really. Some of the most energetic particles scattering off the
ubiquitous but very low energy background.

Anyway, if you propose that this is the mechanism for energy loss and you know
how dense the CMB photons are (which we do very well) then you can predict
interesting things like the maximum distance a cosmic ray can travel before it
runs out of steam entirely, see

<http://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit>

Although i'm not sure how the OMG particle fits in with this scheme yet

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Groxx
I was looking at that too... the trick that I see is that that's a
_statistical_ limit, not a "travel X miles, lose X% energy, no matter what"
limit. It's still entirely possible for a particle to be over the limit, it's
just highly unlikely.

We detect super-energetic particles frequently, but only a couple "over the
limit". Seems to fit the statistical model to me.

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Groxx
A pretty quick read about a super-fast proton detected in 1991, with a nice
set of comparisons to get the point across. Such as that the proton had enough
energy:

 _to light a 40 watt light bulb for more than a second._

Yowza.

That said, included in the article is this:

[Star Trek's best ship would take] _a little more than 21 years [to reach the
center of the galaxy]. By contrast, an observer on board the Oh-My-God
particle would arrive at the nucleus of the Milky Way, according to his clock,
just about 3 seconds after leaving Starbase Terra. That's more than 9,700,000
times faster than the starship._

* bzzzz * wrong. It's only _perceived_ as faster to the riders, the particle takes ~32,000 years (according to their numbers) to do the same trip, which isn't pointed out in that section. At which point our whole civilization is probably dead or passed you by long ago. And they've apparently forgotten about suspended animation.

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fexl
But that's what he said: "according to his [the rider's] clock" it would take
about 3 seconds to reach the center of the Milky Way. So yes, he is talking
about how fast the riders perceive it, which is all they care about, since
they wrote off their entire families for dead before they left.

Now the strange thing about traveling at 1516c (i.e. far greater than the
speed of light), is that the time dilation equation yields an imaginary time,
in this example 1 / sqrt(1 - 1516^2). I'm not sure how that translates into a
perceived travel time of 21 years.

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Dylan16807
Warp engines make a little stable bubble of space and shift what's around it,
so onboard time matches galaxy time, and you can jaunt a significant way
across the galaxy and still be home in a few years Earth time.

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hegemonicon
Unfortunately, there's the small matter of them requiring orders of magnitude
more energy than exists in the universe.

Link to the Alcubierre Drive - <http://en.wikipedia.org/wiki/Alcubierre_drive>

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synnik
Their statement that the scientists looked in the direction from whence the
particle came, but did not see anything should be self-evident. Whatever
caused the particle to be travelling at such speeds would still emit light
at... the speed of light. They would have had to been looking BEFORE detecting
the particle, even if only nanoseconds before.

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ztravis
Perhaps the source might still be emitting photons?

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Aegean
very interesting and also very well told.

