Science & Technology Q&A for Kids (and others) [November 3, 2023]

Stephen Wolfram answers general questions from his viewers about science and technology as part of an unscripted livestream series, also available on YouTube here: https://wolfr.am/youtube-sw-qa Questions include: How is it that animal species all look relatively similar, or at least similar across a breed (ex: dogs, golden retrievers), yet all humans have unique features?​​ - ​What's your intuition for Euler's number, e?​ - In the recent Halloween spirit, is there any science behind ghostly appearances?​ - If an advanced civilization lived on Earth one billion years ago, would there be signs of there existence in today's time?​ - How does photography work? How are we able to capture an image so easily, whether on film or on a phone screen?​ - Kind of a similar topic: how do mirrors reflect images, and can we trust these images or do they change our perception?​ - Is there a number like e or pi that instead of being small (under 10) is big (like over 100)? How do these numbers get specific notation/names?​ - How many digits of pi can you recite at this moment?​