Informal, or extracuricular, science education offers activities aiming at inspiring the participants and eventually engaging them further in either informal or curricular science learning. After-school science clubs, science camps, workshops and many other activities are often considered in this context.
This inspiration and engagement goal makes informal education significantly different compared to formal education. Whereas curricular studies have definite material on which to focus and guarantee student proficiency, informal education’s main objective is student stimulation and excitement evoking student curiosity. Moreover, students are not obligated, and should not be forced, to take part in informal activities. Instead, they should be encouraged to attend by offering the kind of activity which they might like.
Informal science educational activities are quite diverse, having various characteristics, all sorts of "dimensions". To be attractive to as many youth as possible we should offer wide range of programs, wide in all dimensions, allowing students to choose those which fascinate them the most. In what follows, we will illustrate some of the relevant dimensions to be supplemented by examples.

Wide in terms of its content
One of the most important dimensions is the specific science field and topic of the activity. We should offer topics ranging from theoretical math, through basic exact and natural science to applied science and high technology. A wide range of topics in math, physics, chemistry, biology and other sciences would allow many potential students to select their field of interest. Indeed, after-school science clubs and popular science lectures often offer a wide range of topics in each of these sciences. Science camps, workshops and research projects span a wide range as well.
Along with the topic variability one should also consider the level and the type of activity, namely the blend of theoretical study with hands-on activity. Students will not be attracted by too high or low a level activity which might be appropriate for older or younger students. Some students tend to prefer highly theoretical activities, either with or without use of computers, whereas other will not join unless it is a primarily or entirely hands-on activity. Some may even expect tangible products which the student may bring home (Fig. 1).

Fig. 1: Proud participants of a two hour workshop show their hand-made cardboard models. Often a tangible take-home product is useful in inspiring and engaging young participants. The activity was conducted at the students' school by the Science Mobile team.

Yet another important aspect of the content is the competitive element. Many students may prefer activities having no competitive element at all, such as science clubs or popular science lectures. Others are attracted by the opportunity to challenge their peers. They prefer contests such as Olympiads and tournaments. Some programs may include competitive elements though they are not as competitive as indi-vidual contests. Team competitions and tournaments allow sharing the risks and the excitement with team members, thus alleviating some of the competitiveness. Other programs, such as symposia at which the best presenter is selected, are not as competitive as the benefits of attending the symposium might well exceed the best presenter competition.

Where
Naturally the place at which the informal activity takes place is of crucial relevance when potential student participation is considered. Often centers may offer activities at their venue, serving only nearby students within commuting distance. Other activities which may extend for several days or weeks can be offered if proper accommodation is available. Camps and workshop of this type may draw participants from all over the country, or even from abroad. One-time events such as a Science Fair or Science Festival, a one-day symposium or a special lecture may also draw participants living far away, provided they indeed are very attractive.

Fig. 2: Many science centers focus on engaging students in actual research work. In some cases this research is conducted in educational labs, whereas in other cases students join scientists in the research lab.

Traveling activities such as those carried out by Science Mobile teams, lecturers or demonstrators can also be carried out at schools, community centers or similar places at towns far away from the Science Center in charge.
However, when the activity location is considered, the student's home, a train station (or the train itself,) should not be overlooked. Using books and booklets, surface and electronic mail as well as the internet, educators may tailor activities to be carried out everywhere! In fact, nowadays even the virtual cyberspace might provide proper place for informal educational activities.

When
The time of any activity, as well as its duration, is a very important factor when participation is considered. Science clubs are often offered as a sequence of meetings taking place regularly at a specific time, such as once a week, on the same day, hour and place. They often suit students leaving nearby only.
Students leaving far away or nearby students who are busy at the time of the club may still take part in more intensive programs such as workshops or science camps. Typically they are arranged during school vacation and last for several days or weeks.
Some activities may be primarily carried out at home, school or any other place, but do require attendance at the center at least once. Some tournaments, science fairs (in which students present their research), and symposia are of this kind.
Considering time, we should also think about activities for morning hours at which classes may take part (during the school year) and afternoon hours (e.g. science clubs). At night, other activities, such as astronomy club, might be appropriate.
Some activities, such as those conducted via mail or the internet can be carried out not only eve-rywhere but also at any time (as long as the net is connected).
Some activities may offer a very long engage-ment extending for several years. Often participants may be requested to meet several milestones when considering the advancement from one year or one stage to the next.
Finally, considering the time and the duration of an informal educational activity we would like to suggest that it should be planned to promote engagement and activity even beyond its (formal) duration. After all, inspiration, excitement and engagement in science are the rationales of informal science education. This aspect of informal activities should carefully be incorporated into the planning, as it is by no means obvious.

Who
All should be able to participate, or in other words, we should spare no effort to arrange attrac-tive programs for any sector of the population. There should be programs for the gifted, advanced or science enthusiast student, for it is from among them the future scientist, engineers and science professional will emerge.
The underachieving and underserved portion of the population should not be further deprived from science and modern technology. Hence a special effort should be devoted to attracting them to science via informal science education (Fig. 3).

Fig. 3: Proud Ethiopian immigrant mother follows her daughter’s computer work during a special "Parents Day" of an extra-curricular science education program for Ethiopian immigrant students. The program helps motivated and advanced students of Ethiopian origin to get the support other students may have at home. Certain sections of society may need special, custom-made programs to meet their specific needs.

The vast majority of the average students will become the majority of citizens of the future society. They will have to decide and eventually vote on issues which require a certain level of scientific knowledge and acquaintance with scientific thin-king. Contemporary debates about what, if anything, we should do with regard to global warming, mobile phone radiation hazards, risks of using new materials and genetically modified food, underline the basic understanding of science everyone should have presently.

Fig. 4: Four team members in action during the Chemistry Tour-nament. Typically, team contests draw more girls than individual competitions, and among the chemists, they are the majority.

Needless to say that we also should aim at all other sectors of society, minorities included. In many cases special attention should also be paid to the participation of both genders – girls and boys. Occas-ionally, the program should take differences into account. For instance, we found that girls are not as eager to compete individually. Not a single girl took part in our computer science Codeguru individual competition. Hence we arranged another computer science contest, Codeguru Extreme; this team tournament succeeded in drawing female participants. Many girls are also taking part in teams in our Physics and Chemistry Tournaments (Fig. 4).
Another very important, often neglected sector is the adult population. Not only it is important to offer informal science activities for adults helping them better cope with contemporary science and science-related social issues, but also in order that they will be able to share the excitement with the youth in their families. To that end, perhaps the best way is to arrange activities for mixed adult-youth attendance. Our monthly astronomy club meetings serve as a good example of a successful mixed audience program (Fig. 5).

Fig. 5: A moment of excitement among the adult and youth participants of the astronomy club.

Mixed participation of the two genders, various age groups, and various nationalities often enhance the activity, provided proper planning and execution are carried out. There are however, occasions where separate activities for each participant group are more appropriate due to differences in their scientific backgrounds or comprehension, or due to social and cultural constraints.
International participation and the language barrier is yet another dimension. For students sharing the same native language, a program in that language is most natural. Nevertheless, in cases of international participation, the language should be international as well, typically English. Indeed the activity language is yet another "dimension".

Summary

To better comply with its mission, informal science educational organizations should make the effort to offer a wide range of activities – wide in every aspect and dimension. Activities at various levels, diverse scientific fields, and range of competitive nature, should be offered at a variety of theoretical and hands-on combinations.
Activities should be offered to nearby potential participants, but also special efforts should be made in tailoring programs for those who live far away. Special attention should be paid in planning for the various age groups - adults included, to minorities and to both genders Moreover, on many occasions, mixed participation of various age groups, various nationalities and even different fields of interest may be profitable, provided the activity is adapted accordingly.
The location, the time and the duration of the activities should all be considered thoroughly to allow attendance of whoever is interested among the target population. Many activities will take place at a specific center, but schools and community centers all across the country should not be overlooked, and even the participant's own home is an appropriate setting for certain activities.