# Are Aliens Visiting Earth? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [June 25, 2020, 10:13am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949 "2020-06-25T10:13:36Z")\ **Posts on this page:** 20\ **Page:** 20
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 6, 2023, 9:24pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/383 "2023-09-06T21:24:27Z")
> [@beowulff](#): > > I think it’s unlikely that we are very special, but I also think it’s unlikely we will ever find out otherwise. The Universe is too big and too sparse. That is functionally the same as being alone in the universe. If we never find any evidence of any other civilisation in the universe, then we are too far away from any aliens to be affected by them. This is one of the most likely solutions to the Fermi Paradox, but far from being the only one. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [September 6, 2023, 9:46pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/384 "2023-09-06T21:46:24Z")
Believing without (or dispite) solid evidence sounds like religion to me. Not my bag. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 6, 2023, 9:51pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/385 "2023-09-06T21:51:05Z")
Thinking that Humans are special sounds like religion to me. Not my bag. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 6, 2023, 10:19pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/386 "2023-09-06T22:19:26Z")
It’s not a value judgement on “specialness” it’s about being objective about (possibly uncomfortable) facts. I would very much like for their to be other ETIs in our galaxy. It just doesn’t appear to be the case. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 6, 2023, 10:41pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/387 "2023-09-06T22:41:29Z")
That’s because we are blind, not necessarily because there is nothing to see… ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 6, 2023, 10:43pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/388 "2023-09-06T22:43:12Z")
How do you know that? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 6, 2023, 10:50pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/389 "2023-09-06T22:50:47Z")
Well, it’s patently obvious that our ability to see objects in the galaxy is, to be generous, primitive. We don’t have the ability to detect another civilization such as our own if it was on a planet orbiting the nearest star. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [September 6, 2023, 11:08pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/390 "2023-09-06T23:08:23Z")
You’ve said that before, and I think you’re wrong. We’ve measured the chemical composition of a planet 65 light years away - artificial compounds in the atmosphere of a planet around Alpha Centaurus would be detectable, and interpretable as an indication of a technological civilization. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [September 6, 2023, 11:16pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/391 "2023-09-06T23:16:55Z")
I don’t think humans are any more special than cats, rats, bats or platypuses. It is our _planet_ that is unique… until there is evidence to the contrary. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [September 6, 2023, 11:18pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/392 "2023-09-06T23:18:34Z")
Is this another belief? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 7, 2023, 12:04am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/393 "2023-09-07T00:04:58Z")
Cite? ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [September 7, 2023, 12:07am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/394 "2023-09-07T00:07:41Z")
Would you accept an answer of “I just believe it”? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 7, 2023, 12:09am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/395 "2023-09-07T00:09:41Z")
Believe whatever you want… ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 7, 2023, 12:26am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/396 "2023-09-07T00:26:05Z")
> [@beowulff](#): > > We don’t have the ability to detect another civilization such as our own if it was on a planet orbiting the nearest star. Again, the chance of any two civilizations being close to human levels of progress is infinitesimal, let alone _multiple_ civilizations. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [September 7, 2023, 12:26am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/397 "2023-09-07T00:26:08Z")
I am confused. You keep saying that it is a matter of belief, but you ask for a cite when facts are presented. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [September 7, 2023, 12:28am UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/398 "2023-09-07T00:28:26Z")
> **[Carbon Dioxide Detected on Exoplanet HD 189733b](https://www.universetoday.com/22080/carbon-dioxide-detected-on-exoplanet-hd-189733b/)** > > \[/caption\]The Hubble Space Telescope has detected carbon dioxide on a planet orbiting another star. The star in question is HD 189733 (also known as V452 Vulpeculae, a variable star designation), a binary system over 60 light years away, and the... > The Hubble Space Telescope has detected carbon dioxide on a planet orbiting another star. The star in question is HD 189733 (also known as V452 Vulpeculae, a variable star designation), a binary system over 60 light years away, and the planet is approximately the size of Jupiter (called HD 189733b). The exoplanet is already known to contain water and methane molecules from previous Hubble and Spitzer campaigns, but this is the first time CO2 has been discovered ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [September 7, 2023, 6:43pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/399 "2023-09-07T18:43:22Z")
What makes you think multicellular life is an inevitable evolutionary step? ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [September 7, 2023, 11:19pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/400 "2023-09-07T23:19:04Z")
Here’s a [paper](https://arxiv.org/pdf/2102.05027.pdf) on detection of NO2 in exoplanet atmospheres. With current telescopes signals of anomalous NO2 could be made out to 30 light years. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 10, 2023, 6:20pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/401 "2023-09-10T18:20:44Z")
> [@beowulff](#): > > We don’t have the ability to detect another civilization such as our own if it was on a planet orbiting the nearest star. > [@Mijin](#): > > Again, the chance of any two civilizations being close to human levels of progress is infinitesimal, let alone _multiple_ civilizations. This seems to be the clincher. Human civilisation will not continue to exist at a 21st century level of technology for much more than a century; either our civilisation will collapse, or we will continue to progress, potentially for thousands or even millions of years. A civilisation with technology a million years in advance of our own may be easily detectable, especially if it produces lots of waste heat. There have been a number of searches for waste heat signatures with no results - I expect we may find some signatures of this kind in due course, but there do not seem to be any in nearby systems. Other potentially detectable signatures from an advanced civilisation would be radar transmissions, assuming the civilisation has the desire to protect itself against rogue asteroids or unfriendly intruders. Communication transmissions between distant locations within the home system or with probes in surrounding systems could also be detectable in some circumstances. I sometimes wonder if the ‘Wow!’ signal was some kind of probe telephoning home, and we were just coincidentally in the way. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [September 10, 2023, 7:42pm UTC](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949/402 "2023-09-10T19:42:48Z")
Agreed, but I would go further. We aren’t only looking for things that we can conceive of, but _anything whatsoever_. Imagine that there was some helical structure at the edge of our galaxy that was emitting a complex, non-repeating pattern of gamma rays. It would be good evidence of ETIs (it would at least make us consider the possibility) even while we would have no idea of its purpose. But, we don’t see Dyson swarms, we don’t see heat signatures and we don’t see gamma helixes…we don’t see anything at all. Which of course doesn’t rule out advanced ETIs, but it should absolutely make us more pessimistic about how many there might be. [Previous page](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949.md?page=19) [Next page](https://boards.straightdope.com/t/are-aliens-visiting-earth/912949.md?page=21)