Do ALIENS exist? | An astrophysicist's perspective

00:00 - Introduction
00:35 - How many galaxies are in the Universe?
03:19 - How many stars are in the Universe?
04:45 - How many of those have planets?
07:14 - How many of those are habitable?
09:11 - Will we ever communicate with alien life?
13:04 - BLOOPERS

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👩🏽‍💻 I'm Dr Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars.

[Shedding]

The one saddened thought I find is the universe might be teeming with life, however, just in different time periods. As one civilization is born, thrives, and becomes extinct, another one surfaces. Never converging with each other. The number of stars the universe has might be a big number, but it doesn't compare with time. All in all, there might be an intelligent civilization out there at the same moment we are in, but the chances of them being here at the same moment in time, within a distance we can communicate with is very small. This is where the great silence comes in. You would figure if there was millions of civilizations, you would at least hear the after glow of their radio signals even with Doppler shifts in their light and the attenuation of light signals through vast distances, but we have heard, a very disturbing, nothing.

[rankezis]

the fact that im not currently having a full-on existential crisis just speaks to dr becky's skills as a presenter. literally can't stop watching this is my new comfort place on the internet

[SpikeXtreme]

“Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.” - Douglas Adams, The Hitchhikers Guide to the Galaxy.

[notthatdonald]

"either we are alone in the Universe or we are not. Both are equally terrifying.” - Arthur C. Clarke

[OboeCanAm]

"...And pray that there's intelligent life somewhere up in space, 'cause there's bugger all down here on Earth!" - E. Idle

[MikeWood]

When I was in high school in the early 80s, I attended an open lecture by Carl Sagan who was visiting the University of Toronto. His topic: the Drake Equation. There was such a demand for tickets that they held it in Convocation Hall which has a 1700 seat capacity. It was packed. Seeing him talk in person and do the math on a blackboard was completely enthralling. 'Billions and Billions.' :)

[jackbarton]

Oracle, are we alone in the universe?
"Yes. You are alone in the universe."
So there's no one else out there?
"There are others but they are all alone too"

[JRodz-xdxo]

Where were you Dr Becky after all these times? You just came out of thin air and there you're all over the place with wonderful informative videos!! I like them all, also love your accent. Lovely !

[juriskrumgolds]

-Are we alone in the Universe?
-Yes, we are
-So there is no other life in the entire Universe?
-There is. But they are also alone.

[floreaciprian]

Ever since I started to grasp the sheer size of the observable universe it always seemed almost unfathomable for life not to exist on other planets

[okenwaayomikun]

It's like telling the Earth: Love is out there, but you're probably not going to find it.
Damn, the Universe can have a dark sense of humor.

[brianlea]

The best thing about Dr Becky is the BLOOPERS.
Just showing that she can and will make fun of herself.
💕😂😂😘

[MysterySemicolon]

I love how scientists answer this question. Both the question and the answer are simple, but the reasons and method for obtaining the answer are so much more complicated.

[raziqkanani]

great video, I think its also worth noting that all these calculations are based off the assumption that life can only exist in the way we know it. There may be many variations to the requirements for what is required in order for life to take shape across the universe.

[andreav]

The fact that galaxies that are 1e5 light years across are still held together by gravity, making it work at such scale, is mind blowing.

[davidm]

I love how you take us from the smallest unit of which we know, and extrapolate it to the universe that we can see. It makes it a lot more comprehensible.

[PatriciaOConnorBonsaiBalcony]

When we look at the number of things that we have questioned about space over the years and we look at the amount of photo evidence that many times we were, in fact, holding at that same moment but didn't yet know how to be interpreted. These two thoughts combined lead me to wonder how many other civilizations are already in our database and we just don't know what we are looking at

[maximiliankief]

One of my favourite quotes from Star Trek: In this galaxy, there's a mathematical probability of three million Earth-type planets. And in all of the universe, three million million galaxies like this. And in all of that... and perhaps more, only one of each of us.

[Relkond]

100% of explored star systems have life.
Given the sample size (1), there may be some bias to adjust for.

[glickmpb]

Just saw this... One thing I find amazing that, if there is life out there in the universe, it may not at all be life like we know it. You defined the "goldy locks zones", but that does not mean that life could not have evolved elsewhere; only life as we know it. Its fascinating!