Note that there is a duplicate of this question for 2030.

Assume that in January 2021, a message such as email is sent to a group of 25 leading cosmologists (specified later in this question), asking them, "In your opinion, does the current evidence strongly support the conclusion that the universe's expansion is accelerating? To avoid ambiguity, please include 'yes', 'no' or 'other' in your response." This question resolves positively if the majority of those who reply directly to the email respond with a direct "yes" in their reply, and resolves negatively if the majority of those who reply directly respond with a direct "no" in their reply. Replies that do not contain a direct "yes" or direct "no" (including those who say "other") are not counted.

The message is allowed to include an introduction explaining the purpose of the question.

This question resolves ambiguously if any of the following happen:

The replies from such an inquiry are not published by the end of January 2021.
There are an equal number of direct "Yes"s or "No"s in the replies.
A Metaculus moderator believes that all of the responses are too vague to count up the "Yes"s and "No"s.

The group of 25 leading cosmologists would be the group created via the following method. In January 2021, take the most highly cited papers uploaded to arXiv from 2010 to 2020 (inclusive) in the categories "Cosmology and Nongalactic Astrophysics" and "General Relativity and Quantum Cosmology." For each paper, in order from most citations to least citations, add the first author to the group if they are both alive and have a public email address. A person has a public email address if they are associated with a research institution that has a webpage listing their email for contact. Continue adding authors until there are 25 members in the group.

The number of citations for a paper is determined by Google Scholar.