MASSIVE LONG POST WARNING: feel free to skip this

I usually like Vsauce a lot, but I disagree with just about every assumption and every conclusion he makes in this video.

Anthropogenic vs external extinction event -
I think the likelihood of an anthropogenic extinction event is low. Even in the cold war, at the apex of "mutually assured destruction" risk, IF that destruction was triggered I think it would have been extremely unlikely to make humans go extinct. The US and USSR might have nuked each other to near-extinction, but even with fairly mobile nuclear fallout / nuclear winter, etc. I think that enough humans would have remained in other areas to remain a viable population.

Even if ONE single person had access to every single nuclear weapon in existence, and they went nuts and tried to use them ALL with the goal of killing every single human being on the planet, I still bet there would be enough pockets of survivors in remote areas to prevent humans from going utterly extinct.

Sure, an anthropogenic event could be devastating -- catastrophic even -- to human life. But I think humanity could recover even from an event with an associated human death rate of 95% or more -- and I think the likelihood of anything like that is real slim.

So that leaves natural or external extinction events. The KT extinction (end of the dinosaurs) is the most recent major event, and it happened 65 million years ago. Homo sapiens have been around 150-200,000 years, and as a species we've been through some fairly extreme climatic changes. For example, humans survived the last ice age around 10-20,000 years ago -- so even without technology, tools, buildings, etc. we managed to survive a climate shift that extreme. Mammals survived the KT extinction, quite possible that we could have too -- especially if we were to face it with access to modern technology/tools/knowledge/etc.

So I think it would probably take something even more extreme than the asteroid responsible for KT to utterly wipe us out. Events like that are temporally rare enough that I don't think we need to lose any sleep over them. And again, it would take something massive to wipe out more than 95% of the human population. We're spread out, we live in pretty high numbers on basically every landmass on earth (perhaps minus Antarctica), we're adapted to many many different environments ... pretty hard to kill us off entirely.


"Humans are too smart to go extinct" @1:17 -
I think we're too dumb to go extinct. Or at least too lazy. The biggest threats we face are anthropogenic, but even the most driven and intentionally malevolent human or group of humans would have a hard time hunting down *everybody, everywhere*.


Doomsday argument -
I must admit that I don't really understand this one. The guess of how many total humans there will be, EVER, seems extremely arbitrary. But anyway, I tend to think it might fall apart if you try to use it to make the same assertions about, say, bacterial life instead of human life. Some specific species of bacteria have been around for way way longer than humans, and in numbers that dwarf human populations. So, the 100 billionth bacteria didn't end up needing to be worried about its "birth number", nor did the 100 trillionth.


Human extinction "soon" vs. "later" -
Most plausibly likely threats "soon" are anthropogenic. The further we push into "later", the more the balance swings towards external threats, I think. But we're talking about very small probabilities (in my opinion anyway) on either side of the scale. But I don't think that "human ingenuity will always stay one step ahead of any extinction event thrown at it" (@4:54). Increased human ingenuity is directly correlated with increased likelihood of anthropogenic extinction, so that's pretty much the opposite. For external extinction events, I think it is actually fairly hard to imagine some external scenario or event that could have wiped out humans 100, 20, 5, 2, or 1 thousand years ago that wouldn't wipe us out today even with our advances and ingenuity. And anything really bad enough to wipe us out is not going to wait for us to be ready for it...


Fermi paradox -
This is the most reasonable bit of the whole video, but it doesn't present the most common / best response. Other stars, galaxies, etc. are really far away. The Milky Way galaxy is 100,000+ light years across. The nearest other galaxy (Andromeda) is 2.2 million light years away. A living being (or descendents of living beings) coming to us either of those distances would have to survive as long as the entire history of human life, all while moving at near the speed of light, and have set out headed straight for us from the get-go all those millions and millions of years ago. So lack of other visitors is not surprising at all.

Evidence of other life would be far more likely to find, but even that would have to be in a form we could understand. Human radio signals heading out into space are less than 100 years old. Anything sentient and actively looking for us, even within the cosmically *tiny* radius of 100 light years, would have to have to evolved in such a way that they also use radio; otherwise the clearest evidence of US living here on Earth would be undetectable to them. Just because that's what we're looking for, doesn't mean that other intelligent beings would take the same approach.

Add all that up, and I don't think that the Fermi paradox is much cause for alarm. Maybe there are/have been LOTS of intelligent life forms out there, but they have been sending out beacons in formats we don't recognize, or they are simply too far away for those beacons to have reached us yet.


OK, I think I'm done. Clearly I found the video interesting, to post that long of a rambling response... But I was disappointed in it compared to usual Vsauce stuff. Still, upvote for the thoughts provoked and potential discussion, even though I disagree with most of the content and conclusions.

From what I've been taught, it takes infinite energy to accelerate mass to the speed of light, which would mean neutrinos will never reach the speed of light either, maybe close but not fully, unless maybe all the energy in the universe could be utilized to make it happen, and even then it's questionable.

AFAIK, photons have mass, but in a theoretical state of zero velocity they theoretically don't have mass (which can't currently be tested).

As for neutrinos, I said, "at or faster than the speed of light", not "faster than the speed of light". I never claimed they do go faster than the speed of light, because the jury's still out on that one. This is still a debate that divides the physics community and the matter is far from settled.

How about -sometimes photons appear to have mass, sometimes they don't.

As for Neutrinos, apparently they also can't exceed the speed of light. The experiment that said they might was flawed.
http://www.gizmag.com/neutrinos-sub-light-speed/22876/

Umm... photons have mass.

Why is he saying they don't have mass?

Neutrinos also travel at or faster than the speed of light and have mass.

That's pretty much my favourite physics fact right there. From the point of view of a photon, travel is instantaneous. From the sun, from the next nearest star, from the big bang... It seemed to the photon that it was emitted and absorbed instantaneously.

We also had a brilliant bunch of lectures by Don Kurtz who told us about a book called Mr Tompkins in wonderland, in which the narrative was written by a guy who was a bicyclist in a world where the speed of light, c = 10 metres per second or so. http://en.wikipedia.org/wiki/Mr_Tompkins

We then did a bunch of questions about what that man experienced, what colour traffic lights were, what length his bike and roads were, and what time it said on the clock tower. Just great, that's what makes me want to lecture one day.

I admit, i kind of fast forwarded through this one

..and thus traveling faster then the speed of light? Suck it Einstein!

If humans disappeared then nothing. An empty world with nothing happening and no-one to see it. A void sphere expanding out from our solar system at the speed of light with the last of our transmissions, in every direction and forever.

Unless and until sophonce appears again. Then the lights come on and the universe can see itself.

I got all the way to 1:45 and could no longer listen to this clap trap. It's total BS 'science' put forth by someone who obviously does not understand the science he's 'explaining'.
As has been mentioned, nothing was 'dialed in' because physics forces values to remain in a narrow range. That's anthropomorphizing the laws of physics, and is simply ridiculous.
If the speed of light were different by a 'hairs breadth', it would change nothing. (I'll say that definitively because it is different depending on the medium the light travels through, btw)
If gravity were different, yes, the universe might be ever expanding or eventually collapsing, that does not erase the possibility of life, it only puts a time limit on the period that it might exist, under our current understanding of what's required for life. It might not actually limit life at all.
I hate pseudo science videos created by non scientific people with a purpose to confuse other non scientific minds into believing insanity. Downvote!

WOW, that vacuum slowed down the bowling ball to the speed of a feather. Pretty cool. That's why nothing can go faster than the speed of light.

Powers always change depending on what books your reading, but the big difference is that Quicksilver can only move at the speed of sound, and the Flash can move at the speed of light.

Fibre can go a pretty long distance before it affects the signal though...

Fibre is comprised mainly of silicone, the more pure the fibre, the less dispersion issues occur at or around 1550nm (one of the main wavelengths used for long distance transmission, as we can easily and cheaply amplify this using ebrium doped segments and some pumps!)

Any impurities in the fibre will absorb the 1550 at a greater rate than other wavelengths, causing linear distortions in the received carrier along greater distances. This is called Brillouin scattering.

In the context of the above video, consider a paralell cable sending data over 100m. If one of those lines is 98m, then every bit that is sent down that line, will be out of order.

Same deal with Brillouin scattering, only on the optical level. Thats one of the main issues we gotta deal with at distance, however it only ever occurs at or around 1550nm, and only ever when you are driving that carrier at high powers (i.e. launching into the fibre directy from an ebrium doped amplifier at +15 dBm)

Theres some fancy ways of getting around that, but its not cheap.

Anywhere from say around 1260 to 1675nm is the typical bandwidth window we use today.

So, say 415nm of available bandwidth.
If we want that in frequency to figure out the theoritcal bits/sec value from the shannon-hartley theory, then we just take the inverse of the wavelength and times it by the speed of light.

7.2239e+14 hz is the available spectrum.

...thats 7.2239e+5 terahertz....

Assume typical signal to noise on fibre carrier of +6dB (haha, not a chance in hell it would be this good across this much bandwidth, but whatever..)

For a single fibre you would be looking at an average peak bandwidth of around 20280051221451.9 mbps.

Thats 19,340,564 Terabits per second, or 18,887.3 Petabits per second.

You can fudge that +/- a couple of million Tbps based on what the actual SnR would be, but thats your average figure.....thats a lot of Terabits.

On one fibre.

Source: Im a telecoms engineer

To be fair, there are a few good reasons as to why you can make a good case for it being a universal speed limit - time dilation from light's perspective effectively makes travel time over any distance instantaneous so at the speed of light you can travel any distance instantly, making it effectively infinitely fast. Any faster and you could "arrive before you got there." Mass energy relation indicates you'd need an infinite amount of energy to reach light speed. Loads more.

I'd love it all to be wrong though.

"Even at the speed of light, the fastest speed possible..."

That we know of!!!!

Zing!

A string one km long thinner then a single proton has the mass (energy) of the earth and they flop around at almost the speed of light.

Just Wow!