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Warp wrote:
> Xavier Manget <NOS### [at] free fr> wrote:
>> If the trains' speeds are close enough to the speed of light, because of
>> relativistic length contraction (and with correct timing) the trains will
>> have enough length to pass each other on the double track?...
>
>> Did I get it? :-p
>
> Yes.
>
> (Had you heard of the thought experiment, or did you figure it out on
> your own?)
Oh, wait, I thought this was a real-world situation. Silly me.
Regards,
John
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Warp nous apporta ses lumieres en ce 2008/01/02 15:53:
> Darren New <dne### [at] sanrrcom> wrote:
>> It's funny how many people won't deny something unintuitive like quantum
>> mechanics or relativity, stuff that's really hard to understand properly
>> even *with* math, but they're happy to deny the possibility of
>> evolution, which is easy to explain without any mathematics.
>
> That may be because we can check the theory of relativity here and
> now, but we can't go back in time a few million years to check evolution
> nor we can perform evolutionary experiments which require a few millions
> of years.
>
There have been some evolutionary experiments that have been done. Some using
mice, others using insects. Take a mice colony and have it live in a lightless
environment, another in a chilly one, a third in a very hot one, a fourth in a
place where possible living area are far from food sources. Another one
prevented females from copulating for an increasing time.
Do the experiment over a few decades (some are still going on after over a century).
In the dark environment you get mice with atrophied eyes, longer wiskers and
larger ears, and a high albinism incidence.
In the cold, you get longer hairs, increased body fat, short tails and smaller ears.
In the heat, shorter hairs, slightly longer and spindly paws.
The ones that had to travel a lot devoloped longer, stronger legs, larger
stomach. They also devoloped hamster like cheeks.
In the last case, the longevity increased very significantly! Increases in the
order of +200 to 300% to the life span! We are now doing that experiment in a
very large scale: The whole Human Western and Asian populations! Asia, Europe,
the Americas, parts of Africa and Oceanya. From the middle ages to now,
generation time went from about 15 to 16 years to over 30~33 years...
Those are called "forced evolution experiments". The key is to use speciment
that have a short generation time.
--
Alain
-------------------------------------------------
There will always be beer cans rolling on the floor of your car when the boss
asks for a ride home from the office.
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Warp wrote:
> That may be because we can check the theory of relativity here and
> now,
99.44% of the world cannot - they accept the word of experts. And we
can check the theory of evolution here and now - it has been done
repeatedly.
> but we can't go back in time a few million years to check evolution
Sure we can. That's what fossils are for. Same way we check things like
binary stars obeying GR and black holes obeying GR.
> nor we can perform evolutionary experiments which require a few millions
> of years.
Nor can we perform GR experiments that require a few millions of years,
like noticing that the expansion of space seems to be accelerating, or
that light traveling long distances thru space doesn't travel at 'c' for
all the different frequencies.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > That may be because we can check the theory of relativity here and
> > now,
> 99.44% of the world cannot - they accept the word of experts.
It depends on the subject. When the experts say, for example, that they
have to take GR equations into account for GPS to work, that just using
Newtonian laws would not be enough, then sure, you just have to take their
word for it, but it's quite improbable that they are all lying. You can
go and buy a cheap GPS device and check that it works. Now you either
accept that it works correctly because of those GR equations, or you claim
that all the experts are lying. There's no reason why they would do the
latter.
This is an example of a measurement which we can do right here right now.
It doesn't require humongous amounts of time.
As for things like the expansion of the universe, it's a lot more of a
hypothesis. The current consensus among scientists is that the universe
is expanding, but without the millions of years of measurements it's a
lot more of guesswork. I don't believe science says otherwise.
There's a difference between saying "I believe scientists when they say
that GPS needs GR equations to work correctly" and "the current consensus
among scientists is that the universe is expanding". There's a categorical
difference between these two.
Now, if I say "the current consensus among scientists is that the theory
of evolution is mostly correct", that doesn't mean I have the same degree
of confidence in it as with the GPS thing.
> And we
> can check the theory of evolution here and now - it has been done
> repeatedly.
In the exact same way as we cannot check how the expansion of the
universe has occurred during millions of years, we cannot check how
evolution has occurred during millions of years. We can speculate from
some of the consequences, but it's only speculation. We cannot measure
here and now.
> > but we can't go back in time a few million years to check evolution
> Sure we can. That's what fossils are for. Same way we check things like
> binary stars obeying GR and black holes obeying GR.
Says the person who takes expansion of the universe and dark energy
with a grain of salt, and seriously considers alternative theories...
--
- Warp
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John VanSickle <evi### [at] hotmailcom> wrote:
> Oh, wait, I thought this was a real-world situation. Silly me.
Given the proper circumstances (not actual trains, but something similar,
capable of doing the feat), why wouldn't it be a real-world situation?
Or are you saying that relativity doesn't work in the real world?
--
- Warp
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Warp wrote:
> This is an example of a measurement which we can do right here right now.
> It doesn't require humongous amounts of time.
Yep.
> Now, if I say "the current consensus among scientists is that the theory
> of evolution is mostly correct", that doesn't mean I have the same degree
> of confidence in it as with the GPS thing.
Yeah, until you get drug-resistant TB. Then you're kind of screwed.
> In the exact same way as we cannot check how the expansion of the
> universe has occurred during millions of years, we cannot check how
> evolution has occurred during millions of years. We can speculate from
> some of the consequences, but it's only speculation. We cannot measure
> here and now.
Fair enough. But you're not checking that GR worked for millions of
years. You can't check that *any* theory has been correct for millions
of years. It's nothing specific to evolution.
You can watch evolution and speciation in the lab. You can cause it to
happen at will. You can see millions of years of results consistent with
evolution, from bone shape to genetics. You can prove that bone shape
is *caused* by genetics.[1] You have to account for it when creating
medicines. Software and hardware you use daily is designed with
evolutionary algorithms.
Not sure how you can't measure "here and now" what evolution does.
What part do you think is in doubt?
>>> but we can't go back in time a few million years to check evolution
>
>> Sure we can. That's what fossils are for. Same way we check things like
>> binary stars obeying GR and black holes obeying GR.
>
> Says the person who takes expansion of the universe and dark energy
> with a grain of salt, and seriously considers alternative theories...
Yep. Because we have tons of other ways of checking the same thing.
That's what makes it a theory instead of a hypothesis: You get the same
answer when you measure the value with a dozen different independent
experiments.
[1] Apparently, the same gene that causes there to be five fingers is
also related to sexual reproduction, so almost all mammals, birds, and
fish that have anything even remotely like hands and feet, wings,
flippers, fins, etc have five bones in them. Not something you'd expect,
until you look at the genes that cause that, and see they also cause
stuff necessary for sexual reproduction.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Alain <ele### [at] netscapenet> wrote:
> There have been some evolutionary experiments that have been done.
So, how many fish have they converted into cats like this?
(I hope you get the point.)
--
- Warp
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Warp wrote:
> Says the person who takes expansion of the universe and dark energy
> with a grain of salt, and seriously considers alternative theories...
Or, as an alternate way of saying this, when Sharper Image sells a
device that lets me park three cars in a two-car garage by using dark
energy, I'll suspect very strongly the cosmologists have figured it out. :-)
Now, I know very little about cosmology, and that's probably where my
skepticism comes from. But as far as I know, there's really only one
major measurement made post-hoc that supports these theories.
"Inflation" hasn't *predicted* anything, and "dark energy" hasn't
*predicted* anything. Dark matter hypothesis predicted that we'd see
colliding galaxies with the dark matter "splashing" off, as was in the
news recently.
I'd be happy to hear about other things that the hypotheses of
"inflation" or "dark energy" have predicted that were observed only
after those hypotheses were proposed. It would greatly reduce my
skepticism. :-)
> We cannot measure here and now.
We can. We can make predictions of what we'll find based on the theory,
and then when those predictions come true, it supports the theory. Such
as using genetics of different whales to figure out what the genetics of
the first cetacean would have been like, then finding the land animal
with the closest genetics, then digging around for fossils there and
finding fossils of cetaceans with feet near the shore.
Kind of like how Young Earth Creationists have a difficult time figuring
out where the oil is before they start drilling, ya know.
(To be completely clear, I'm not certain that evolution explains
*everything*. But it clearly (to me) explains the majority of what we're
seeing going on, with a large variety of correct predictions.)
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Warp wrote:
> Alain <ele### [at] netscapenet> wrote:
>> There have been some evolutionary experiments that have been done.
>
> So, how many fish have they converted into cats like this?
>
> (I hope you get the point.)
It takes a long time to convert a fish into a cat. So?
How many complete orbits of pluto have been observed? How do you know it
is really orbiting the sun?
You haven't said why you think it's unlikely to be true.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Warp nous apporta ses lumieres en ce 2008/01/03 01:50:
> John VanSickle <evi### [at] hotmailcom> wrote:
>> Oh, wait, I thought this was a real-world situation. Silly me.
>
> Given the proper circumstances (not actual trains, but something similar,
> capable of doing the feat), why wouldn't it be a real-world situation?
>
> Or are you saying that relativity doesn't work in the real world?
>
Real word trains can't go fast enough. A freight train 2000m long going twice as
fast as the fastest maglev will only have a relavistic contraction of atomic
scale, and a thermal expantion from air friction aproaching 1m.
So, your relativistic seppd solution is not viable. My critical breaking
solution is at least tryable. Each wagon coupling can contract almost 30cm,
multiply that by the number of wagons in a typical freight train, and the train
can contract a few meters.
--
Alain
-------------------------------------------------
Methodist: It's not so bad if shit happens, as long as you serve grape juice
with it.
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